Endocrine abnormalities and bone loss in ageing men

Except after orchiectomy, men do not have an equivalent of the rapid phase of bone loss that women experience following menopause. After accounting for the absence of this phase, the patterns of late bone loss and of the increases in serum PTH and bone resorption markers in ageing men are virtually superimposable upon those occurring in women (Riggs et al 1998). In the past, it has been difficult to attribute male bone loss to sex steroid deficiency because men do not have an equivalent of menopause, and because serum total testosterone levels

decrease only marginally with age except for a small subset of elderly men who develop clinical hypogonadism. However, in the last 5 years, thinking on this issue has undergone a sea change.

First, in population studies, we (Khosla et al 1998) and others have shown that although levels of serum total testosterone and oestrogen decrease only slightly in men with ageing, there are major decreases in biologically available levels of both sex steroids (Table 4, Figs 3 and 4). This disassociation is due to a progressive increase in men in levels of the fraction of sex steroids bound to serum sex hormone binding globulin (SHBG) (Fig. 5) which is not available to tissues. The

Age, yrs Age, yrs

FIG. 3. Changes in serum testosterone (T) in ageing men. The left panel shows that serum total testosterone decreases only slightly in ageing men. Total T (P <0.001), bioavailable T (P<0.001). The right panel shows the changes in serum bioavailable testosterone, which decreased progressively with ageing. Values for premenopausal (Pre) and postmenopausal (Post) women are given for comparison. Error bars represent SEM. (With permission from Riggs et al 2000.)

Age, yrs Age, yrs

FIG. 3. Changes in serum testosterone (T) in ageing men. The left panel shows that serum total testosterone decreases only slightly in ageing men. Total T (P <0.001), bioavailable T (P<0.001). The right panel shows the changes in serum bioavailable testosterone, which decreased progressively with ageing. Values for premenopausal (Pre) and postmenopausal (Post) women are given for comparison. Error bars represent SEM. (With permission from Riggs et al 2000.)

FIG. 4. Changes in serum oestrogen (E) in ageing men. The left panel shows that serum total oestrogen decreases only slightly in ageing men. Total E (not significant), bioavailable E (P <0.001). The right panel shows the changes in serum bioavailable oestrogen, which decreased progressively with ageing. Values for premenopausal (Pre) and postmenopausal (Post) women are given for comparison. Error bars represent SEM. (With permission from Riggs et al 2000.)

FIG. 4. Changes in serum oestrogen (E) in ageing men. The left panel shows that serum total oestrogen decreases only slightly in ageing men. Total E (not significant), bioavailable E (P <0.001). The right panel shows the changes in serum bioavailable oestrogen, which decreased progressively with ageing. Values for premenopausal (Pre) and postmenopausal (Post) women are given for comparison. Error bars represent SEM. (With permission from Riggs et al 2000.)